Be careful with that older 50mm 1.4, the AF motor is basically made of glass and breaks constantly. For a crowded dinner, 50mm might still feel a bit tight on your 90D. I would suggest checking out the Sigma 30mm f/1.4 DC HSM Art instead. It’s killer for indoor portraits where you cant move back. If money is tight, just grab the Canon EF 50mm f/1.8 STM because its way more reliable.

Regarding what #2 said about "The Canon EF 35mm f/2 IS USM is a decent option," I totally agree. I've used that glass on my 90D for ages and I'm super satisfied with it. It really is the sweet spot for crop sensors when you're stuck in a tight restaurant. No complaints about the sharpness at all, even wide open. It's a solid workhorse lens for sure. Since you mentioned that 450 dollar budget, you could honestly pick up that 35mm and still have cash left for a Canon EF 50mm f/1.8 STM just to have that extra reach in your bag for headshots.

• Keep your shutter speed at least 1/125 to stop motion blur from people moving their heads while talking.
• Toggle your ISO to auto but cap it at 3200 to keep those 90D files looking clean. Ngl, that 35mm stays on my camera most of the time now. It just works well.

> So now Im thinking maybe the 50mm f/1.4 instead but Ive heard the AF is kinda flaky on the older ones. Man, I feel your pain. I have been struggling with this exact same dilemma for my 90D for months now and its basically the reason I havent taken a single decent indoor portrait lately. I actually tried that older Canon 50mm once for a small gathering and unfortunately, it was a complete letdown. The focus just hunted and hunted in the dim light of the restaurant... so many missed shots of my niece. I think I read somewhere that the third-party brands like Sigma might handle the focus better on these high-res crop sensors, but honestly I am not totally sure if thats just talk. I remember someone on a different thread saying the older Canon glass just isnt as good as we expected it to be once you move up to the 90D sensor. Its super frustrating because I want to stay loyal to the brand but I am just not seeing the reliability I need compared to what my friends get with their setups. Not sure what the right move is but yeah, you are definitely not alone in being stuck here.

The Canon EF 35mm f/2 IS USM is a decent option. It gives a 56mm equivalent view and has fast AF, plus the IS helps with low-light dinner shots indoors... definitely solid.

Wait real quick, are you planning on doing mostly single person portraits or are people gonna be bunched up at the tables? Just trying to get a feel for the space. This whole situation actually reminds me of when my sister asked me to shoot her engagement party at this tiny Italian place downtown. I was all stressed about which lens to bring and then my favorite prime started acting up right as we walked in. The autofocus kept hunting and I spent the first twenty minutes just shaking the camera hoping it would wake up. It was so embarrassing standing there while everyone was waiting to eat their pasta... luckily my cousin had a point-and-shoot in her purse but man, it really makes you realize how much you need gear you can actually trust when you're under pressure like that.